Generation of Unique Chicken Antibodies for Therapeutic Use

Abstract

Chickens possess a unique immune system that allows for production of antibodies by mechanisms typically not seen in mammals. These include the deposition of antibodies into the egg yolk for developing chicks, the dependence on gene conversion as the primary source of antibody diversity, the divergence of the avian and mammalian antibody genomes, and the ability of IgY to withstand the harsh gut environment. These features make chickens an interesting model for therapeutic antibody development to treat and prevent enteric infectious disease, including rotavirus (RV). RV is a leading cause of severe gastroenteritis in humans and animals. Infection results in severe diarrhea, dehydration, and in some cases, death. The purpose of this work was to harness the unique characteristics of the chicken humoral immune system to generate high affinity polyclonal and monoclonal antibodies capable of treating or preventing rotavirus infection. In the first study, we demonstrated the effective use of electron beam inactivation of a pathogen to generate high-titered, neutralizing egg yolk antibodies against the human rotavirus (HRV) G1P[8] strain. Both serum and egg yolk IgY were effective at neutralizing HRV in vitro. Because of the substantial sequence homology observed between human and equine rotaviruses and potential for cross-protection, we developed an egg yolk antibody product for rotaviral diarrhea treatment in foals. Both the serum and egg yolk antibodies were effective at neutralizing ERV in vitro. Egg yolk antibodies were lyophilized and safely administered to foals with group A rotaviral diarrhea in a pilot study. No significant difference was observed between egg yolk antibody treatment and standard diarrheal care. To enhance the specific therapeutic efficacy per mg IgY administered, we pursued the development of an HRV-neutralizing monoclonal antibody (mAb) using single B-cell cloning. This antibody demonstrated considerable recognition of the virus but was ineffective at neutralizing HRV in vitro under the conditions used for testing. Although additional optimization of the single B-cell isolation is warranted, this study reported on the first use of single B-cell cloning in chickens. Altogether, this work demonstrated the advantages of chicken antibody production and provided novel approaches for therapeutic development.